Coated articles having low-E coatings are known in the art. For example, see the following U.S. Patent Documents which describe low-E coatings and which are all incorporated herein by reference in their entireties: U.S. Pat. Nos. 6,686,050, 6,749,941, 6,863,928, 7,166,359, 7,390,572, 7,462,398, 7,534,496, 7,597,962, 7,597,963, 7,655,313, 7,771,830, 7,858,191, 7,879,448, 7,897,260, 7,998,320, and 8,017,243. A low-E coating is for the purpose of providing efficient solar control in applications such as windows, and includes at least one IR reflecting layer sandwiched between two contact layers. The contact layers which sandwich an IR reflecting layer therebetween are sometimes referred to as barrier layers. The contact layer directly below and contacting an IR reflecting layer is often of a material such as ZnO, NiCr, or NiCrOx, and the contact layer directly over and contacting an IR reflecting layer is often of a material such as NiCr or NiCrOx. The contact/barrier layer provided directly over and contacting an IR reflecting layer is for protecting the IR reflecting layer from aggressive environments during sputtering of overlying layers as well as during the lifetime of the coating, and for providing adhesion between the IR reflecting layer and an overlying dielectric layer. However, in order to meet typically desired transmission and optical requirements of low-E coatings, the contact layer provided over an IR reflecting layer generally needs to be very thin. Thin upper contact/barrier layers can often provide sufficient durability when the coating is used in the interior of an insulating glass (IG) window unit where the coating is not directly exposed to the environment. However, for monolithic applications where the coating is directly exposed to the environment (either directly exposed to the interior of a building or home, or directly exposed to the exterior atmosphere), a thin upper contact/barrier layer is sometimes not sufficient by itself to protect the IR reflecting layer (e.g., silver layer) against environmental attacks.
Thus, while conventional low-E coatings provide efficient solar control and are overall good coatings, they are sometimes lacking in terms of one or more of: (a) corrosion resistance to acid and/or alkaline solutions (e.g., 80% HCl boil test and/or 20% NaOH boil test); (b) mechanical performance such as scratch resistance; and/or (c) durability. Accordingly, there exists a need in the art for a coated article that includes a low-E coating and which has improved durability characteristics, but which still is capable of acceptable thermal performance (e.g., blocking a reasonable amount of IR radiation) and/or heat treatment (HT). It is a purpose of this invention to fulfill at least one of the above-listed needs, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.
In certain example embodiments of this invention, an improved overcoat is provided for a low-E coating in order to improve its overall durability. In certain example embodiments the low-E coating may include at least one infrared (IR) reflecting layer of a material such as silver, and the overcoat for protecting the low-E coating includes two spaced apart layers of or including zirconium oxide, where the two zirconium oxide inclusive layers are spaced apart by at least one dielectric layer. In certain example embodiments, the dielectric layer provided between the two layers comprising zirconium oxide may be of silicon oxynitride, silicon nitride, silicon oxide, and/or the like. In certain example embodiments, the two zirconium oxide inclusive layers of the overcoat are not in contact with any metallic or substantially metallic IR reflecting layer (e.g., is not in contact with any Ag-based or Au-based layer). In certain example embodiments, the two zirconium oxide (e.g., ZrO2) inclusive layers of the overcoat are dielectric layers. In certain example embodiments, in the overcoat, one of the layers comprising zirconium oxide (e.g., ZrO2) may be the uppermost layer of the coating relative to the underlying substrate that supports the coating. It has surprisingly been found that such an overcoat improves the durability of the coating in terms of protection of the IR reflecting layer(s) from chemicals, scratches, scratch corrosion, fingerprint corrosion, environmental damage and mechanical damage. Such coated articles may be used in the context of monolithic windows, insulating glass (IG) window units, laminated windows, and/or other suitable applications.
The coated article may or may not be heat treated (e.g., thermally tempered) in different embodiments of this invention. The heat treatment (HT) may be for at least about 5 minutes at a temperature(s) of at least about 580 degrees C., so as to be sufficient for thermal tempering or the like. It has surprisingly been found that such an overcoat discussed herein improves the durability of the coating in terms of protection of the IR reflecting layer(s) from chemicals, scratches, scratch corrosion, fingerprint corrosion, environmental damage and mechanical damage, for the coating both before and after any optional HT.
In certain example embodiments of this invention, there is provided a coated article including a layer system supported by a glass substrate, the layer system comprising: a first dielectric layer on the glass substrate; an IR reflecting layer comprising silver on the glass substrate over at least the first dielectric layer; a contact layer on the glass substrate over and directly contacting the IR reflecting layer; a first layer comprising zirconium oxide on the glass substrate over at least the contact layer; a second dielectric layer on the glass substrate over the first layer comprising zirconium oxide; and a second layer comprising zirconium oxide on the glass substrate over at least the second dielectric layer, wherein the second dielectric layer directly contacts one or both of the first and second layers comprising zirconium oxide.
In certain example embodiments of this invention, there is provided a coated article including a layer system supported by a glass substrate, the layer system comprising: a first dielectric layer on the glass substrate; an infrared (IR) reflecting layer comprising silver on the glass substrate over at least the first dielectric layer; a contact layer on the glass substrate over and directly contacting the IR reflecting layer; a layer comprising NbZr on the glass substrate over at least the contact layer; and an overcoat comprising first and second spaced apart layers comprising zirconium oxide on the glass substrate over at least the layer comprising NbZr.